Semiconductor processing for forming capacitors by etching polysilicon and coating layer formed over the polysilicon

ABSTRACT

In one aspect, the invention includes: a) forming a first opening into a substrate surface; b) forming a polysilicon layer over the substrate surface and within the first opening to a thickness which less than completely fills the first opening to leave a second opening within the first opening; c) forming a coating layer over the polysilicon layer and within the second opening; d) etching the coating layer and the polysilicon layer to remove the coating layer and the polysilicon layer from over the substrate surface and leave the coating layer and the polysilicon layer within the opening; and e) after the etching, removing the coating layer from within the opening. In another aspect, the invention includes: a) forming a first opening into a substrate surface; b) forming a polysilicon layer over the substrate surface and within the first opening to a thickness which less than completely fills the first opening to leave a second opening within the first opening, the polysilicon having a surface with a first degree of roughness; c) forming a coating layer over the polysilicon layer and within the second opening, the coating layer having a surface with a second degree of roughness which is less than the first degree of roughness; d) etching the coating layer and the polysilicon layer to remove the coating layer and the polysilicon layer from over the substrate surface and leave the coating layer and the polysilicon layer within the opening; and e) after the etching, removing the coating layer from within the opening.

TECHNICAL FIELD

The invention pertains to semiconductor processing methods, such as, forexample, methods of forming capacitors.

BACKGROUND OF THE INVENTION

A semiconductor wafer fragment 10 comprising a prior art capacitorconstruction is illustrated in FIG. 1. Wafer fragment 10 comprises asubstrate 12. Substrate 12 can comprise, for example, a monocrystallinesilicon wafer lightly doped with a conductivity-enhancing dopant. To aidin interpretation of the claims that follow, the term "semiconductivesubstrate" is defined to mean any construction comprising semiconductivematerial, including, but not limited to, bulk semiconductive materialssuch as a semiconductive wafer (either alone or in assemblies comprisingother materials thereon), and semiconductive material layers (eitheralone or in assemblies comprising other materials). The term "substrate"refers to any supporting structure, including, but not limited to, thesemiconductive substrates described above.

An insulative material layer 14 is formed over substrate 12. Layer 14can comprise, for example, borophosphosilicate glass (BPSG). Anelectrical node 16 is formed within substrate 12. Node 16 can comprise,for example, a diffusion region formed by implantingconductivity-enhancing dopant within substrate 12.

An opening extends through layer 14, and a container-type capacitorassembly 20 extends within the opening. Capacitor assembly 20 comprisesa storage node 18, a dielectric layer 22, and a capacitor plate 24.Storage node 18 can comprise, for example, conductively-doped ruggedpolysilicon, wherein rugged polysilicon is defined to encompasshemispherical grain polysilicon and cylindrical grain polysilicon.Dielectric layer 22 typically comprises a composite of silicon oxide andsilicon nitride. Capacitor plate 24 typically comprisesconductively-doped polysilicon. Storage node 18 is in electricalconnection with electrical node 16.

A difficulty in forming capacitor assembly 20 arises in forming storagenode 18. Formation of storage node 18 typically comprises providingconductively-doped hemispherical grain polysilicon within the openingand over layer 14. The hemispherical grain polysilicon is subsequentlyetched to leave the hemispherical grain polysilicon remaining only inthe opening. During such etching, conductive polysilicon particulatescan be formed. Such particulates can redeposit on wafer 10 to causeshorts in an integrated circuit formed on wafer 10. For instance, it iscommon in semiconductive processing to form multiple capacitorassemblies 20 on a single semiconductive wafer. Conductive polysiliconparticles formed during etching of a hemispherical grain polysiliconlayer can redeposit between adjacent capacitor structures to form ashort between the capacitor structures. It would be desirable to developalternative methods for forming a capacitor structure wherein ahemispherical grain polysilicon layer is etched to form a storage nodewithout having conductive polysilicon particles redepositing andshorting electrical components.

SUMMARY OF THE INVENTION

In one aspect, the invention includes a semiconductor processing methodwherein a first opening is formed into a substrate surface. Apolysilicon layer is formed over the substrate surface and within thefirst opening to a thickness which less than completely fills the firstopening to leave a second opening within the first opening. A coatinglayer is formed over the polysilicon layer and within the secondopening. The coating layer is provided to a thickness which less thancompletely fills the second opening. The coating layer and thepolysilicon layer are etched to remove the coating layer and thepolysilicon layer from over the substrate surface and to leave thecoating layer and the polysilicon layer within the opening. After theetching, the coating layer is removed from within the opening.

In another aspect, the invention includes a semiconductor processingmethod wherein a substrate having a surface is provided. A first openingis formed in the substrate and through the surface. A roughenedpolysilicon layer is formed over the substrate surface and within thefirst opening. The polysilicon layer is formed to a thickness which lessthan completely fills the first opening to leave a second opening withinthe first opening. A coating layer is formed over the polysilicon layerand within the opening. The coating layer and the polysilicon layer areetched to remove the coating layer and the polysilicon layer from overthe substrate surface and to leave the coating layer and the polysiliconlayer within the opening. After the etching, the coating layer isremoved from within the opening.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a fragmentary, diagrammatic cross-sectional view of asemiconductive wafer fragment comprising a prior art capacitor assembly.

FIG. 2 is a diagrammatic, fragmentary, cross-sectional view of asemiconductive wafer fragment at a preliminary processing step inaccordance with a method of the present invention.

FIG. 3 is a view of the FIG. 2 wafer fragment at a processing stepsubsequent to that shown in FIG. 2.

FIG. 4 is a view of the FIG. 2 wafer fragment at a processing stepsubsequent to that shown in FIG. 3.

FIG. 5 is a view of the FIG. 2 wafer fragment at a processing stepsubsequent to that shown in FIG. 4.

FIG. 6 is a view of the FIG. 2 wafer fragment at a processing stepsubsequent to that shown in FIG. 5.

FIG. 7 is a view of the FIG. 2 wafer fragment at a processing stepsubsequent to that shown in FIG. 6.

FIG. 8 is a view of the FIG. 2 wafer fragment at a processing stepsubsequent to that shown in FIG. 7.

FIG. 9 is a view of the FIG. 2 wafer fragment at a processing stepsubsequent to that shown in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws "to promote the progressof science and useful arts" (Article 1, Section 8).

A semiconductor processing method of the present invention is describedwith reference to FIGS. 2-9. Referring to FIG. 2, a semiconductor waferfragment 40 is shown at a preliminary processing step. Wafer fragment 40comprises a substrate 42 and a layer 44 overlying substrate 42. Layer 44comprises an upper surface 45. A node location 46 is defined withinsubstrate 42. Substrate 42 can comprise, for example, monocrystallinesilicon lightly doped with a conductivity-enhancing dopant. Layer 44 cancomprise, for example, an insulative material, such as BPSG. It is notedthat, as discussed above in the background section, the term "substrate"as utilized in this application is a general term. Accordingly, layer 44can be referred to as a substrate in the claims that follow.

Referring to FIG. 3, a first opening 48 is formed through layer 44 andto node location 46. Opening 48 can be formed by conventional methods.

Referring to FIG. 4, a semiconductive material layer 50 is formed overlayer 44 and within opening 48 (shown in FIG. 3). Layer 50 is formed toa thickness which less than completely fills opening 48 to leave asecond opening 52 within first opening 48. Layer 50 preferably comprisespolysilicon, and more preferably comprises rugged polysilicon, such ashemispherical grain polysilicon. Layer 50 can be formed by methods knownto persons of ordinary skill in the art, such as by chemical vapordeposition of hemispherical grain polysilicon. The deposited polysiliconcan be in situ doped, or can be doped subsequently, such as byimplanting.

Polysilicon layer 50 contacts node location 46. Node location 46 can be,for example, a conductively doped diffusion region. Such diffusionregion can be formed, for example, by implanting conductivity-enhancingdopant into opening 48 (shown in FIG. 3). Alternatively, such diffusionregion can be formed at later processing steps, such as, for example, byout-diffusion of conductivity-enhancing dopant from doped polysiliconlayer 50.

Referring to FIG. 5, a coating layer 54 is formed over semiconductivematerial layer 50 and within second opening 52 (shown in FIG. 4).Coating layer 54 is preferably provided to a thickness which less thancompletely fills second opening 52 to form a third opening 56 within thesecond opening. As will become apparent from the discussion below,coating layer 54 is a sacrificial layer. Accordingly, it is preferred tokeep layer 54 thin, as it more expedient to remove a thin layer than athick layer.

In preferred embodiments, wherein semiconductive layer 50 comprisesrugged polysilicon, coating layer 54 can comprise either an organicmaterial or an inorganic material. Example inorganic materials aresilicon dioxide and other silane oxides (SiH₄ --N₂ O). Example organicmaterials are photoresist and amorphous carbon. Coating layer 54 can,for example, consist essentially of photoresist. If coating layer 54comprises photoresist, it preferably is applied conformally over anunderlying surface and is much thinner than conventional photoresistlayers utilized for capacitor fabrication. One method for forming athinner layer of photoresist is to start with a photoresist having alower viscosity than the photoresists conventionally utilized forcapacitor fabrication. Conventional photoresist utilized for capacitorfabrication typically is applied to be about 9,500 Angstroms thick. Aconventional photoresist can comprise, for example, a product marketedas Shipley SPR 950 by Shipley Co. of 455 Forest St., Marlboro, Miss.01752. In contrast, a coating layer 54 of the present inventionpreferably is preferably applied to a thickness of less than 3,000Angstroms, and more preferably of less than 2,500 Angstroms. Forinstance, the photoresist can be OCG 895 purchased from OlinMicroelectronic Materials of Providence, R.I., which is typicallyprovided to a thickness of about 2,200 Angstroms, or AZ BARL from AZPhotoresist Products of Sunnyvale, Calif., which is typically providedto a thickness of about 1,100 Angstroms.

Referring to FIG. 6, semiconductive material layer 50 and overlyinglayer 54 are etched to remove layers 54 and 50 from over insulativematerial layer 44, and to leave layers 54 and 50 within opening 48(shown in FIG. 3). The etching preferably removes coating layer 54 andsemiconductive material layer 50 at about an equivalent rate. An exampleetch chemistry for removing photoresist and rugged polysilicon at abouta 1:1 rate is to use an etchant comprising NF₃, He and O₂ (20:14:6) inan Applied Materials 5000 Etch System. If the organic material isamorphous carbon, a similar etch can be used to that described above forphotoresist. If the coating layer comprises an oxide, a suitable etchchemistry for achieving approximately equal rates of oxide removal andrugged polysilicon removal utilizes a 50 sccm (standard cubic centimeterper minute) flow of CF₄, a 15 sccm flow of CHF₃, a pressure of 200mTorr, and a power of 750 watts in an Applied Materials 5000.

When coating layer 54 and material 50 are removed at a substantiallyequal rate, coating layer 54 can support particles of layer 50 as theparticles are removed. In a preferred process, rugged polysilicon layer50 comprises a first degree of surface roughness, and coating layer 54comprises a second degree of surface roughness which is less than thefirst degree of roughness. Such second degree of roughness can be moreeasily etched without forming undesired large pieces which can fall backon wafer 40 and interconnect electrical components. Accordingly, etchingthrough the relatively smooth surface of 54 and into layer 50 with anetch that etches the two at a substantially equivalent rate can reducethe amount of large particulate material formed from the etch process.

In alternative embodiments of the invention which are not shown, coatinglayer 54 can be provided to a thickness which completely fills opening52 (shown in FIG. 4). Coating layer 54 can then be etched with a rapidremoval process to reduce a thickness of layer 54 to less than about2,300 Angstroms such that layer 54 is reduced to a thickness which lessthan completely fills opening 52 (shown in FIG. 4) to form third opening56. A method for rapid removal of an organic material, such asphotoresist, utilizes an oxygen plasma (O₂) or O₂ with a small amount ofa fluorine containing gas, such as, for example, NF₃ or CF₄. A methodfor rapid removal of an inorganic material, such as silicon dioxide,utilizes a CF₄ /CHF₃ plasma. After the thickness of layer 54 is reduced,the etch chemistry can be changed to a chemistry which removes material54 and semiconductive material 50 at an approximately equivalent rate.

The etch of layers 54 and 50 can be monitored by conventional methods todetermine when the etch reaches upper surface 45 of layer 44. Afterupper surface 45 is reached, etching is preferably continued for alimited time to recess layers 50 and 54 beneath upper surface 45, asshown in FIG. 7.

Referring to FIG. 8, coating layer 54 is selectively removed relative tosemiconductive material layer 50. A method for selectively removing aphotoresist layer 54 relative to a polysilicon layer 50 is oxygen plasmaetching. A method for selectively removing an amorphous carbon layer 54relative to a polysilicon layer 50 is oxygen plasma ashing. A method forselectively removing a silicon dioxide layer 54 relative to apolysilicon layer 50 is a hydrofluoric acid bath.

Referring to FIG. 9, semiconductive material layer 50 is incorporatedinto a capacitor construction 60. Specifically, a dielectric layer 62 isformed over layer 50, and an overlying capacitor plate 64 is formed overdielectric layer 62. In the shown capacitor construction 60,semiconductive material layer 50 is a capacitor storage node. Dielectriclayer 62 and cell plate layer 64 can be formed by conventional methods.Storage node 50 is in electrical contact with electrical node location46. Electrical node location 46 can be in electrical contact with othercomponents of an integrated circuit (not shown) on wafer 40 toelectrically interconnect capacitor assembly 60 with such otherelectrical components.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

We claim:
 1. A semiconductor processing method comprising:forming afirst opening into a substrate surface; forming a polysilicon layer overthe substrate surface and within the first opening to a thickness whichless than completely fills the first opening to leave a second openingwithin the first opening; forming a coating layer over the polysiliconlayer and within the second opening, the coating layer being provided toa thickness which less than completely fills the second opening; etchingthe coating layer and the polysilicon layer to remove the coating layerand the polysilicon layer from over the substrate surface and leave thecoating layer and the polysilicon layer within the opening; and afterthe etching, removing the coating layer from within the opening.
 2. Themethod of claim 1 wherein the coating layer comprises an organicmaterial.
 3. The method of claim 1 wherein the coating layer comprisesan inorganic material.
 4. The method of claim 1 wherein the coatinglayer comprises silicon dioxide.
 5. The method of claim 1 wherein thecoating layer comprises photoresist.
 6. The method of claim 1 whereinthe coating layer comprises amorphous carbon.
 7. The method of claim 1wherein the coating layer consists essentially of photoresist.
 8. Themethod of claim 1 wherein the etching removes the coating layer and thepolysilicon layer at about a same rate.
 9. A semiconductor processingmethod comprising:forming a first opening into a substrate surface;forming a semiconductive material layer over the substrate surface andwithin the first opening to a thickness which less than completely fillsthe first opening to leave a second opening within the first opening;forming a coating layer over the semiconductive material layer andwithin the second opening, the coating layer being formed to a thicknessof less than 3000 Angstroms, and less than completely filling the secondopening; etching the coating layer and the semiconductive material layerto remove the coating layer and the semiconductive material layer fromover the substrate surface and leave the coating layer and thesemiconductive material layer within the opening; and after the etching,removing the coating layer from within the opening.
 10. A semiconductorprocessing method comprising:forming a first opening into a substratesurface; forming a polysilicon layer over the substrate surface andwithin the first opening to a thickness which less than completely fillsthe first opening to leave a second opening within the first opening,the polysilicon having a surface with a first degree of roughness;forming a coating layer over the polysilicon layer and within the secondopening, the coating layer having a surface with a second degree ofroughness which is less than the first degree of roughness; etching thecoating layer and the polysilicon layer to remove the coating layer andthe polysilicon layer from over the substrate surface and leave thecoating layer and the polysilicon layer within the opening; and afterthe etching, removing the coating layer from within the opening.
 11. Themethod of claim 10 wherein the coating layer is formed to a thickness ofless than 3000 Angstroms.
 12. The method of claim 10 wherein the coatinglayer comprises an organic material.
 13. The method of claim 10 whereinthe coating layer comprises an inorganic material.
 14. The method ofclaim 10 wherein the coating layer comprises silicon dioxide.
 15. Themethod of claim 10 wherein the coating layer comprises photoresist oramorphous carbon.
 16. The method of claim 10 wherein the coating layerconsists essentially of photoresist.
 17. The method of claim 10 whereinthe etching etches the coating layer and the polysilicon layer at abouta same rate.
 18. The method of claim 10 wherein the coating layercomprises silicon dioxide, and wherein the etching comprising etchingwith an etchant comprising CF₄ and CHF₃.
 19. The method of claim 10wherein the coating layer comprises photoresist; and wherein the etchingcomprising etching with an etchant comprising NF₃, He and O₂.
 20. Themethod of claim 10 wherein the etching etches the coating layer and thepolysilicon layer within the opening to a level beneath the substratesurface.
 21. The method of claim 10 wherein the coating layer isprovided to a thickness which less than completely fills the secondopening.
 22. The method of claim 10 wherein the coating layer isprovided to a thickness which completely fills the second opening; themethod further comprising, before etching the polysilicon layer and thecoating layer, removing some of the coating layer from within the secondopening.
 23. The method of claim 10 wherein the coating layer isprovided to a thickness which completely fills the second opening andwherein the etching comprises:etching the coating layer faster than thepolysilicon to reduce a thickness of the coating layer to less thanabout 2300 Angstroms; and after etching the coating layer to a thicknessof less than about 2300 Angstroms, etching the coating layer and thepolysilicon layer at about a same rate.
 24. The method of claim 10wherein the coating layer comprises photoresist and is provided to athickness which completely fills the second opening and wherein theetching comprises:etching the coating layer with O₂ to etch the coatinglayer faster than the polysilicon, the etching reducing a thickness ofthe coating layer to less than about 2300 Angstroms; and after etchingthe coating layer to a thickness of less than about 2300 Angstroms,etching the coating layer and the polysilicon layer at about a same ratewith an etchant comprising NF₃, He and O₂.
 25. The method of claim 10wherein the coating layer comprises oxide and is provided to a thicknesswhich completely fills the second opening and wherein the etchingcomprises:etching the coating layer with CF₄ and CHF₃ to etch thecoating layer faster than the polysilicon, the etching reducing athickness of the coating layer to less than about 2300 Angstroms; andafter etching the coating layer to a thickness of less than about 2300Angstroms, etching the coating layer and the polysilicon layer at abouta same rate with an etchant comprising CF₄.
 26. A semiconductorprocessing method comprising:providing a substrate having a surface;forming a first opening in the substrate and through the surface;forming a roughened polysilicon layer over the substrate surface andwithin the first opening, the polysilicon layer being formed to athickness which less than completely fills the first opening to leave asecond opening within the first opening; forming a coating layer overthe polysilicon layer and within the second opening; etching the coatinglayer and the polysilicon layer to entirely remove the coating layer andthe polysilicon layer from over the substrate surface and leave thecoating layer within the second opening and the polysilicon layer withinthe first opening, wherein the etching etches the coating layer and thepolysilicon layer at about a same rate; and after the etching, removingthe coating layer from within the second opening.
 27. The method ofclaim 26 wherein the coating layer comprises an organic material. 28.The method of claim 26 wherein the coating layer comprises an inorganicmaterial.
 29. A semiconductor processing method comprising:providing asubstrate having a surface; forming a first opening in the substrate andthrough the surface; forming a roughened polysilicon layer over thesubstrate surface and within the first opening, the polysilicon layerbeing formed to a thickness which less than completely fills the firstopening to leave a second opening within the first opening; forming acoating layer over the polysilicon layer and within the second opening,the coating layer comprising silicon dioxide; etching the coating layerand the polysilicon layer to entirely remove the coating layer and thepolysilicon layer from over the substrate surface and leave thepolysilicon layer within the first opening and the coating layer withinthe second opening wherein the etching etches the coating layer and thepolysilicon layer at about a same rate; and after the etching, removingthe coating layer from within the second opening.
 30. The method ofclaim 26 wherein the coating layer comprises photoresist or amorphouscarbon.
 31. The method of claim 26 wherein the etching etches thecoating layer within the second opening, and the roughened polysiliconlayer within the first opening to a level beneath the substrate surface.32. A semiconductor processing method comprising:providing a substratehaving a surface; forming a first opening in the substrate and throughthe surface; forming a roughened polysilicon layer over the substratesurface and within the first opening, the polysilicon layer being formedto a thickness which less than completely fills the first opening toleave a second opening within the first opening; forming a coating layerover the polysilicon layer and within the second opening, the coatinglayer being provided to a thickness which less than completely fills thesecond opening; etching the coating layer and the polysilicon layer toremove the coating layer and the polysilicon layer from over thesubstrate surface and leave the polysilicon layer within the firstopening and the coating layer within the second opening; and after theetching, removing the coating layer from within the second opening. 33.A semiconductor processing method comprising:providing a substratehaving a surface; forming a first opening in the substrate and throughthe surface; forming a roughened polysilicon layer over the substratesurface and within the first opening, the polysilicon layer being formedto a thickness which less than completely fills the first opening toleave a second opening within the first opening; forming a coating layerover the polysilicon layer and within the second opening, the coatinglayer being provided to a thickness which completely fills the secondopening; etching the coating layer with a first etch that removes thecoating layer more rapidly than the polysilicon layer to reduce athickness of the coating layer; after reducing the thickness of thecoating layer, etching the coating layer and the polysilicon layer witha second etch to remove the coating layer and the polysilicon layer fromover the substrate surface and leave the polysilicon layer within thefirst opening and the coating layer within the second opening; and afterthe etching, removing the coating layer from within the second opening.34. A method of forming a capacitor comprising:providing a substratehaving a surface; forming a first opening in the substrate and throughthe surface; forming a roughened polysilicon layer over the substratesurface and within the first opening, the polysilicon layer being formedto a thickness which less than completely fills the first opening toleave a second opening within the first opening; forming a coating layerover the polysilicon layer and within the second opening; etching thecoating layer and the polysilicon layer to remove the coating layer andthe polysilicon layer from over the substrate surface and leave thecoating layer within the second opening and the polysilicon layer withinthe first opening, wherein the etching etches the coating layer and thepolysilicon layer at about a same rate; after the etching, removing thecoating layer from within the second opening to leave the roughenedpolysilicon within the first opening, the roughened polysilicon withinthe first opening being a storage node; forming a dielectric layer overthe storage node; forming a capacitor plate over the dielectric layer;and providing an electrical node in electrical contact with the storagenode.
 35. The method of claim 34 wherein the coating layer comprises anorganic material.
 36. The method of claim 34 wherein the coating layercomprises an inorganic material.
 37. The method of claim 34 wherein thecoating layer comprises silicon dioxide.
 38. The method of claim 34wherein the coating layer comprises photoresist.
 39. The method of claim34 wherein the coating layer comprises amorphous carbon.
 40. The methodof claim 34 wherein the etching etches the coating layer and theroughened polysilicon layer within the opening to a level beneath thesubstrate surface.
 41. The method of claim 34 wherein the coating layeris provided to a thickness which less than completely fills the secondopening.
 42. The method of claim 34 wherein the coating layer isprovided to a thickness which completely fills the second opening; themethod further comprising, before etching the polysilicon layer and thecoating layer, removing some of the coating layer from within the secondopening.